The present invention relates to a fast neutron nuclear reactor of the type comprising a primary circuit integrated into a liquid metal-filled vessel and containing the reactor core, as well as primary pumps for bringing about the circulation of said liquid metal and means for transferring the heat carried by the liquid metal to the water circulating in a water/steam circuit having means for converting said heat into electricity.
In existing reactors of this type, such as the French Phenix and Super-Phenix reactors, the heat carried by the liquid metal of the primary circuit (generally sodium) is transferred to the water of a water/steam circuit by an intermediate circuit, called the secondary circuit. A liquid metal (generally sodium) circulating in the secondary circuit removes the heat carried by the primary liquid metal in heat exchangers integrated into the reactor vessel and transfers it to the water of the water/steam circuit by steam generators outside the vessel.
In these reactors, the liquid metal secondary circuit is provided so that there is no risk of contact taking place between the sodium of the primary circuit and the water of the water/steam circuit within the actual reactor vessel. Thus, it is known that a violent reaction is brought about by contact between the sodium and the water. In a fast neutron nuclear reactor, such a contact can occur at the steam generators. In order to prevent the shock wave resulting from a sodium - water reaction having repercussions up to the reactor core, it has been decided to position the steam generators outside the reactor vessel.
In parallel, the existing reactors such as the French Phenix and Super-Phenix reactors are of the integrated type, in which the complete primary circuit is confined within the reactor vessel. This option has been chosen to take account of the fact that it is always preferable to confine a radioactive primary circuit both for radiation protection and security reasons.
Bearing in mind these two opposing requirements, the existing integrated fast neutron reactors consequently comprise an intermediate liquid metal circuit, so that costs are significantly increased.
Therefore, consideration has been given to the elimination of the intermediate liquid metal circuit by removing the primary circuit from the reactor vessel. However, this solution is not completely satisfactory, due to the high radioactivity of the fission products entrained by the primary liquid metal.